 @mixin hairline-common {
    position: absolute;
    box-sizing: border-box;
    transform-origin: center; /* cover wechat button:after default transforn-origin */
    content: ' ';
    pointer-events: none;
  }
  
  @mixin hairline($border-color:#ddd) {
     @include hairline-common();
  
    top: -50%;
    right: -50%;
    bottom: -50%;
    left: -50%;
    border: 0 solid $border-color;
    transform: scale(0.5);
  }
  
  @mixin hairline-bottom($border-color: #ddd, $left: 0) {
    @include hairline-common();
  
    top: auto;
    right: 0;
    bottom: 0;
    left: $left;
    border-bottom: 1px solid $border-color;
    transform: scaleY(0.5);
  }
  